Maternal-embryo interaction leading up to the initiation of implantation of pregnancy in cattle

Abstract

Early embryo development following fertilization occurs in the oviduct. However, despite being the site of fertilization in cattle, it is possible to by-pass the oviduct by producing embryos in vitro and/or by transferring blastocysts recovered from one female into the uterus of another. While there is substantial evidence for the oviduct having an influence on the quality of the developing embryo, manifested in altered morphology, gene expression and cryotolerance, evidence for a two-way dialogue is weak. In contrast, successful growth and development of the post-hatching blastocyst and pregnancy establishment are a result of the two-way interaction between a competent embryo and a receptive uterine environment. Progesterone (P4) plays a key role in reproductive events associated with establishment and maintenance of pregnancy through its action on the uterine endometrium. Elevated concentrations of circulating P4 in the immediate post-conception period have been associated with an advancement of conceptus elongation, an increase in interferon-tau production and, in some studies, higher pregnancy rates in cattle. This review summarizes current knowledge on the communication between the developing embryo and the maternal reproductive tract.

PGF2α levels in Day 8 blood plasma are increased by the presence of one or more embryos in the uterus

“…In particular, concentrations of PGF 2 α normally exceed several times that of PGE 2 (Bartol et al, 1981;Lewis et al, 1982;Shelton et al, 1990;Ulbrich et al, 2009). At such stages, PGs activate a number of IFNT-stimulated genes, and it seems that PGs could be important recognition signalling molecules in cattle (Spencer et al, 2013;Lonergan and Forde, 2014). In contrast with these observations later in development, our results in blood on Day 8 showed that ZE embryos did not affect PGE 2 concentrations.…”

BVDV alters uterine prostaglandin production during pregnancy recognition in cows

“…Regulation of the synthesis and release of PGE 2 and PGF 2α are crucial to this process (Bazer 2013, Lonergan & Forde 2014. Failure of PR is a significant risk factor for embryonic mortality (Diskin et al 2011, Forde et al 2011.…”

“…Following successful ovulation and subsequent fertilisation, production of interferon-τ (IFNT) by the trophectoderm begins at around day 8 of gestation and increases dramatically during conceptus elongation (Kimura et al 2004). A sufficient threshold level of IFNT must be reached by day 16 to ensure pregnancy recognition (PR) and prevention of luteolysis (Forde et al 2011, Lonergan & Forde 2014. IFNT acts in a paracrine manner on the uterine endometrium to develop a receptive environment.…”

“…IFNT acts in a paracrine manner on the uterine endometrium to develop a receptive environment. This involves changes in the uterine epithelium that are tightly regulated by steroid hormones, type I interferons, cytokines, prostaglandins (PGs) and growth factors and their receptors (Forde et al 2011, Dorniak et al 2012, Lonergan & Forde 2014.…”

Editorial: International Cow Fertility Conference ‘New Science – New Practices’ in Westport, Ireland, in 2014

“…Lonergan and Forde (2014) conclude that while there is substantial evidence for the oviduct having an influence on the quality of the developing embryo, evidence for a two-way dialogue is weak. However, successful growth and development of the posthatching blastocyst and pregnancy establishment are a result of the two-way interaction between a competent embryo and a receptive uterine environment.…”